If you ask me, i think it should be
A: Divided into several classes, ie Medic, heavy inf., light inf., recon, sniper.
B: Once you choose your class, there is a set of weapons unique to that class - ie only the light inf. can choose a garand or a Carbine or a Gewehr or a mauser.
Only a scout can choose a thompson or an mp40, etc.
C: You choose your sidearms RS style.
Then, if you wanted to get ultra realistic, you could make it so each side only has a set stockpile of weapons and ammo, and when you run out of a certain gun or a certain ammo, phwoosh, you outta luck.
However, you gain ammo with each kill your team makes!
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Penis There, i said it. Are you happy now?